381. For starters, cabin pressures at high altitudes are set at roughly what they would be if you lived at 5,000 to 8,000 feet above sea level.

译文

对于初试者，高空舱内压力被大体设定为相当于居住在海拔5000到8000英尺处所承受的压力。

点睛

what引导的是介词at的宾语从句，what在从句中充当表语。
high altitudes意为“高空，高海拔地区”。如：
This type of breathing is not considered abnormal at high altitudes. 这种呼吸在高海拔地区不被看成是不正常的。
sea level意为“海平面”。如：
The top of the hill is just 50 meters above sea level. 这座小山的山顶只有海拔50米。

考点归纳

有关set的常见短语为：
be (all) set for sth./to do sth.意为“准备好（做）某事”。如：
We are all set for victory in the election. 我们决意要在选举中获胜。
He was set to go when the bell rang. 他准备好要走时，门铃响了。
set sth. aside意为“把某事物放在一边；节省或保留出”。如：
He set aside his book and lit a cigarette. 他把书放到一边，点了一支烟。
You should set aside a few minutes each day to do some exercises. 你应该每天抽出一些时间来锻炼一下身体。
set off意为“开始”。如：
We'd better set off for the station immediately. 我们最好立刻动身去火车站。